CN111904420A

CN111904420A - Magnetic resonance tomography system

Info

Publication number: CN111904420A
Application number: CN202010380706.0A
Authority: CN
Inventors: 斯特凡·波佩斯库
Original assignee: Siemens Healthcare GmbH
Current assignee: Siemens Healthcare GmbH
Priority date: 2019-05-09
Filing date: 2020-05-08
Publication date: 2020-11-10
Also published as: EP3736590B1; US11340321B2; EP3736590A1; US20200355764A1; EP3736590B8

Abstract

The invention relates to a magnetic resonance tomography system (1) comprising a basic field magnet arrangement (4) for generating a basic magnetic field (B0) and a plurality of spatially separated measurement locations (M1, M2, M3, M4, M5, M6, Mp, Ms), wherein the magnetic resonance tomography system (1) is designed to use a conventional basic magnetic field (B0) jointly for the measurement locations (M1, M2, M3, M4, M5, M6, Mp, Ms). Furthermore, the invention relates to a measuring device (12, 12p, 12s) for a magnetic resonance tomography system (1) and to a method for measuring raw data recorded by a magnetic resonance tomography.

Description

Magnetic resonance tomography system

Technical Field

The invention relates to a magnetic resonance tomography system ("MR system"), a measuring device for a magnetic resonance tomography system and a method for measuring raw data recorded by a magnetic resonance tomography.

Background

Today, whole-body MR scanners belong to the most expensive equipment for medical imaging at a cost of sometimes millions of euros. The scanners typically use strong superconducting magnets, which can well have a weight of several tons. The manufacturing and operating costs of such magnets are typically between 70% and 80% of the total system cost.

The basic magnetic field generated by the device is so strong that it can also accelerate metal objects strongly, such as for example a patient chair in the examination space. In the early eighties, MR scanners were generally unshielded and the magnet volume was sized extremely large (2 to 4 times as large as the imaging volume) in order to detect large stray magnetic fields. The region of the stray field is the so-called "controlled region" in which the static magnetic field has a strength greater than 0.5G or 50 μ T.

To reduce stray fields, modern actively shielded basic field magnet configurations include at least one additional set of magnet coils that resist the external magnetic field generated by the main coil. For example, the main winding can generate a basic magnetic field of 2.0T, while the shield coil generates a field of 0.5T in the opposite direction. The net effect is a basic field of 1.5T in the middle of the basic field magnet. Although the shield reduces the effective field strength in the working volume, the reduction effect on the stray field is significantly greater. However, this significantly reduces the efficiency of the basic field magnet, which requires higher currents through the magnet coils and/or a higher number of windings per coil. Both of which add to the cost.

In order to keep the costs low, the manufacturer must increase the length of the basic field magnet and limit the opening of the patient tunnel (English: "bore"). Thus, however, a whole-body MR scanner encloses the patient into the narrowest space. This is a major problem for patients with claustrophobia, which affects and limits MR use. Clinical studies have demonstrated that up to 15% of all MR patients suffer from claustrophobia-based anxiety state and either cannot be examined or require sedation. In 8 million MR procedures per year worldwide, about 2 million MR examinations are not completed due to claustrophobia. In economic terms, this corresponds to a loss of 10 hundred million euros, assuming a price of 500 — > cents per program.

Another disadvantage is that access to the patient by medical personnel during imaging is very limited or impossible due to the magnetic field and stenosis. This has hitherto led to: interventional MRI has not to date had significant clinical applications.

From the prior art a large number of experiments are known which show a number of configurations with low magnetic fields and open magnets with the following objective: reduce magnet cost, improve the effect of approaching the patient or avoiding claustrophobia. Typically, the scanners use either permanent magnets or electromagnets that operate at room temperature. The static magnetic field strength is much lower than 0.5T.

In general, the imaging volume of alternative scanners is strongly limited because the magnetic poles are very close to the patient's body, which is contradictory to the goal of open access or as unrestricted a patient space as possible. For example, US 2004/0066194 a1 discloses MR scanner architectures that are unilateral or in a patient table. However, due to the small electromagnet, the magnetic field strength of the static basic magnetic field B0 is strongly reduced here when spaced apart from the basic field magnet. The magnetic field strength is from 0.5T on the magnet surface up to 0.05T with 30cm (factor x 10 over a gap of 30 cm). Furthermore, a heavy electromagnet with a heavy iron yoke is required for such a magnet, which considerably limits the access to the patient. Furthermore, the magnetic field is strongly non-linear and anisotropic in all spatial directions. Another disadvantage is that the imaging volume is limited to about 30 x 20 cm.

Furthermore, non-superconducting electromagnets heat up during operation and require active cooling. To avoid ion contamination, this is usually achieved by means of hollow conductors and water treatment systems, which also limit the openness of the scanner.

Disclosure of Invention

It is an object of the present invention to provide an alternative magnetic resonance tomography system, by means of which the above-mentioned disadvantages can be avoided or at least reduced.

The object is achieved by a magnetic resonance tomography system, a measuring device for use in a magnetic resonance tomography system and a method for measuring raw data recorded by a magnetic resonance tomography.

The magnetic resonance tomography system according to the invention comprises a basic field magnet arrangement for generating a basic magnetic field (which basic field magnet arrangement can also be referred to as "basic field magnet system") and a plurality of spatially separated measurement sites.

The basic field magnet arrangement comprises a basic field magnet which generates a desired basic magnetic field. This can be, for example, a known basic field magnet in the form of a solenoid. The measurement site is designed for performing MR measurements and therefore comprises (at least temporarily as explained further below) the infrastructure required for this purpose, for example the measurement devices mentioned. In this connection, the measurement location can also be referred to as a "magnetic resonance measurement location" (MR measurement location) in order to emphasize the situation.

It is essential to the invention that the magnetic resonance tomography system is designed such that the expected basic magnetic fields are jointly used (intentionally or deliberately) at the measurement site. Thus, instead of simply two separate MR systems being available, the same basic magnetic field is used. Two different magnetic fields, for example of two MR systems which are completely separate in themselves and have independent basic field magnet systems whose stray fields (which as mentioned above are usually strongly reduced by suitable shielding) may unintentionally or randomly interfere with one another, are not part of the invention. Preferably, the shielding can be omitted in the case of basic field magnets or can be at least weaker than normal, in order, for example, to shield the basic magnetic field outside the region of action in which the measurement site is located.

The invention thus enables an additional examination to be performed in parallel with the magnetic resonance tomography recording or MR examination, as will be explained in more detail later on. This means that on the one hand more patients can be examined and the return on the cost of the MR system is started faster. On the other hand, this offers the possibility of: the number of MR measurement sites available can also be increased in areas of low economic strength. The resource consumption for each MR measurement site can also be reduced.

For this purpose, the preferred magnetic resonance tomography system therefore comprises at least two measuring devices which are designed at least for receiving MR signals, i.e. for acquiring raw data. Preferably, the measuring device is also designed for applying a pulse sequence for the excitation in order to induce MR signals. In this case, each of the measuring devices is designed to carry out a measurement within the scope of the magnetic resonance tomography recording at one of the measuring locations, which are preferably independent of one another and can possibly also be carried out simultaneously, as explained in more detail below.

The measuring device according to the invention for measuring at a measuring site by means of a magnetic resonance tomography system according to the invention comprises: at least one RF transmission system (e.g. a transmission antenna and a transmitter) and an RF reception system (e.g. a reception antenna and a receiver), and preferably additionally a gradient system (in particular an unshielded gradient system at the secondary measurement site) and/or a shim coil system. The RF transmission system and the RF reception system can also have in part common components, for example using a common RF transmission/reception coil. Depending on the configuration, the RF transmission and/or RF reception system of the measuring device can have a whole-body coil or a local coil. Depending on the type of the measuring location, the measuring device can also be designed as a mobile measuring device, so that the measuring location provided for this purpose is equipped with the measuring device at least temporarily during the execution of the magnetic resonance tomography recording. A gradient system or shim coil system which can also be used as a shim coil system is advantageous in particular in the "secondary" measurement locations which are explained in more detail later, since the shim coil system or gradient system can compensate there for undesired inhomogeneities in the stray magnetic field.

The mobile aspect of the measuring device can be embodied in such a way that the measuring device is designed such that it can be gripped or carried in the hand. Preferably, the dimensions of the measuring device are less than 20cm x 20cm, and the weight of the measuring device is preferably less than 5 kg. This is fully achievable since, as already described above, the shielding can be discarded to the greatest possible extent. Only one RF shield is advantageous for a mobile measuring device on almost all sides. In this case, a region should not be shielded by means of the RF shield, whereby the region can be used as a measurement region. Despite the shielding of the measuring device itself, it is advantageous to examine the patient by means of the measuring device in an RF shielded space or a correspondingly shielded chamber.

The measuring device can be controlled by a (possibly superordinate) control device with regard to the course or timing of the measuring step, wherein such a control device is preferably configured such that coordination of a plurality of measuring devices can be achieved. Such preferred control means are described in more detail below. In this context, a centrally coordinated control is very advantageous. In particular, it is particularly preferred in this respect to calibrate the gradients of the individual measurements such that the measurements do not influence one another, for example.

The method according to the invention for measuring raw data for magnetic resonance tomography recording, in particular for magnetic resonance tomography imaging, comprises the following steps:

at least one object is positioned in a measurement site of the magnetic resonance tomography system according to the invention. The object can in particular be a patient or a subject, but can also be an inanimate object, for example a phantom.

Generating a basic magnetic field by means of a basic field magnet arrangement of the magnetic resonance tomography system.

-measuring the raw data. Whereby at least one region of interest (RoI) representing the object is excited by means of a usual MR of suitable RF signals and the MR signals thus induced from the RoI are detected (acquired). The location coding can be carried out by means of inhomogeneities of the basic magnetic field and/or by means of additional gradient fields. After appropriate processing, these raw data are preferably used for imaging, i.e. for generating magnetic resonance image data, but can also be used for other results.

As this will be explained in more detail later on, and also according to various embodiments, the invention also relates in particular to the use of stray magnetic fields of the basic magnetic field (which are generated for the "primary" measurement site itself and have their "main field region" here) for carrying out the measurement of raw data at a "secondary" measurement site, which is arranged in the stray or stray field region of the basic magnetic field. The basic magnetic Field in the intended measurement range or "Field of View" (FOV) is considered here as the main Field region. The measurement region can also be referred to as an "imaging volume". The basic magnetic field in a sphere of about 50cm in diameter in the center of the measurement region is preferably considered as the main field region and the remaining regions of the magnetic field as stray field regions.

In order to control all components of the basic field magnet arrangement and the measuring arrangement(s) of the magnetic resonance tomography system, the magnetic resonance tomography system can have a control device, wherein, as mentioned, the control device can also be configured such that the measurements are coordinated at different measuring points.

According to a preferred embodiment, the control device of the MR system is designed to coordinate the measuring devices such that they coordinate the timing of the measurements at the different measuring locations such that no interference occurs between the measurements. In particular, the influence of field fluctuations (for example caused by gradients) on the measurement can thereby be minimized.

A part of the components of the control device, in particular those responsible for coordinating the measurements, can be implemented in the form of software modules, either entirely or partially, in the processor of the respective control device of the MR system. The large-scale software implementation of such components has the following advantages: the control device which has been used up to now can also be retrofitted in a simple manner by means of a software update in order to operate in the manner according to the invention.

The control device can also comprise a plurality of sub-control devices which are associated, for example, with different measuring points and/or measuring devices and can communicate with one another, preferably for coordination purposes, and/or be coordinated by a superordinate main control unit. The measuring device can therefore in particular also have its own control unit, in particular also a sequence control unit and possibly even its own reconstruction unit.

Further, particularly advantageous embodiments and refinements of the invention emerge from the following description, wherein embodiments of one category can also be modified analogously to embodiments and description of another category, and individual features of different embodiments or modifications can also be combined, in particular, into new embodiments or modifications.

As mentioned, the preferred magnetic resonance tomography system is designed to be able to simultaneously carry out measurements for magnetic resonance tomography recordings at least two of the measurement locations in the common basic magnetic field. This means that two objects can be examined simultaneously at the measurement site, or that further measurements may be able to be performed. However, for this purpose it is not mandatory: raw data measurements, i.e. RF excitation and/or raw data acquisition, must be performed simultaneously, which can also be coordinated in a suitable manner, e.g. nested.

In this connection, "magnetic resonance tomography recording is carried out simultaneously" is therefore to be understood as meaning that the following time periods, in which all measures belonging to a typical MR measurement fall, belong to the "magnetic resonance tomography recording" (also sometimes referred to simply as "imaging"): positioning the patient, possibly applying a contrast agent, applying a pulse sequence, measuring the MR signals, and possibly reconstructing an image, allowing the patient to leave the examination space, etc., i.e. taking up all procedures of the MR system. In this case, the raw data measurement, as part of the magnetic resonance tomography recording, comprises only the application of pulse sequences or RF excitations and the measurement of the MR signals induced thereby. The detection of the MR signals themselves is also described as "raw data acquisition".

Thus, performing magnetic resonance tomography recordings simultaneously means that the time periods of imaging at different measurement locations can coincide or overlap in time. In this case, it may be advantageous if active processes (active procedure) which can influence the magnetic field or another measurement are carried out independently of one another within the time interval of the common requirement. As mentioned, Passive processes (Passive procedure), i.e. processes which do not influence another measurement, such as, for example, the advance of a patient table or the administration of a contrast agent, can generally be carried out completely simultaneously. However, this does not exclude: depending on the arrangement and configuration of the measurement locations relative to one another, it is also possible to carry out active process or raw data measurements simultaneously at different measurement locations.

For example, it is possible to measure alternately in order to avoid mutual interference, that is to say always to carry out a measurement at one of the measurement locations (i.e. to transmit RF pulses and to acquire raw data) and to just position the patient, to move the position of the patient or to administer a contrast agent at the other of the measurement locations. It is known that the preparation and post-processing time of the examination procedure of course also blocks the magnetic resonance tomography system for a considerable period of time, which may be used more efficiently.

A preferred magnetic resonance tomography system according to the first preferred main variant comprises: a special basic magnetic field arrangement and a plurality of measurement sites within the "main field region" of the basic magnetic field arrangement or even within the basic field magnet arrangement itself.

The preferred basic field magnet arrangement has a plurality of spatially separated (active) basic field magnet segments in order to generate (in operation) a desired magnetic field with a defined segment main field direction in each case.

The basic field magnet section is part of a basic field magnet arrangement and comprises at least one basic field magnet defined by at least one magnet coil. However, it is also possible to couple a plurality of individual basic field magnets or magnet coils to form basic field magnet sections. Even if yokes in the basic field magnet are not excluded, it is advantageous, at least for some applications, to construct the basic field magnet as light as possible, i.e. to discard the yokes. That is, the magnet coils of the basic field magnet segments are preferably ironless, possibly forming a free space with in the core region, or the basic field magnet segments are preferably ironless yokes. The basic field magnet can be configured as a conventional electromagnet or as a superconducting electromagnet. Since the magnet coils of the basic field magnets are important here, the basic field magnet sections can also be referred to as "basic field magnet coil sections", in particular.

The "expected" magnetic field (and the expected basic magnetic field) is the magnetic field that is formed in the expected operation of the magnet, i.e. when a current flows through the magnet. The shape is fixedly preset by the design of the magnet, wherein the strength of the expected magnetic field is scaled in strength with different current strengths. Since helmholtz coils are generally used in the technical field of MR systems, the expected magnetic field of the basic field magnet is mostly that of a solenoid. The expected magnetic field of the basic field magnet segments or of the basic field magnet arrangement can be more complex, at least when the basic field magnet segments have a shape which differs from the shape of the helmholtz coil.

The "main field direction" of the magnetic field of the magnet is shown by the vector characterizing the magnetic field stretch within the magnet. Therefore, stray fields are not taken into account, but fields of primary importance in the context of known MR systems. In a solenoidal magnet, the main field direction is perpendicular to the end face of the magnet (solenoid), and in a ring magnet, the main field direction of the magnetic field inside the magnet shows a circular trajectory. In the case of arbitrarily shaped magnets, the main field direction reflects the stretch of the resulting magnetic field vector of the strongest part of the magnetic field (without stray fields). The mentioned section main field direction is the main field direction of the magnetic field of the basic field magnet section.

In a preferred basic field magnet arrangement, at least two of the basic field magnet sections are arranged relative to one another in such a way that their intended main field directions of the magnetic field run at an angle of deflection relative to one another. The deflection angle is of course greater than 0 ° here, since otherwise no deflection is possible. Furthermore, the associated basic field magnet sections are arranged relative to one another in such a way that the expected magnetic field of the basic field magnet sections results in an expected basic magnetic field (of the basic field magnet arrangement). The basic field magnet sections thus together form the basic magnetic field during operation.

The basic field magnet sections are arranged such that the basic magnetic field has a basic magnet main field direction with a ring-shaped extent.

Here, "annular" describes a closed extension, preferably in a single spatial plane, preferably in a circle or at least one shape with rounded corners. Such a toroidal magnetic field has a smaller stray field than the magnetic field of a conventional solenoid. The smaller the stray field becomes, the more basic field magnet sections are used, or the larger the basic field magnet sections are expanded in the direction of the magnetic field expansion. The overall weight of the preferred basic field magnet arrangement is many times smaller than that of C-magnets, in particular because the iron yoke, which is usually required in C-magnets, can be dispensed with here in order to reduce stray fields.

Preferably, magnetic resonance tomography recordings can thus be performed in parallel at more than one measurement site within a common ring-shaped basic magnetic field (i.e. in the main field region of the basic magnetic field).

Particularly preferably, a "ring" magnetic field is referred to herein. In addition to the (substantially circular) ring-shaped magnetic field itself, in particular other magnetic fields which are closed in themselves, having an elliptical, rectangular shape with rounded corners or a shape consisting of circular segments and an "interposed" straight channel (in particular the shape of a simple racetrack with a 180 ° turn and two oppositely directed straight segments), are also considered to be "ring" magnetic fields, i.e. magnetic fields which resemble the magnetic field of a ring.

According to a particularly preferred embodiment, such a basic field magnet arrangement comprises at least three basic field magnet segments (preferably at least four, more preferably at least six or particularly preferably at least eight) which are arranged such that the basic magnet main field direction has the shape of a planar ring, preferably a substantially ring-shaped or ring-like shape, in particular a ring shape with an interposed linear channel (see above). This means that the segment main field directions of the magnetic fields of the basic field magnet segments all lie in a single common spatial plane.

Preferably, the deflection angle of the main field direction of the segment between at least two adjacent basic field magnet segments is at least 5 °, preferably at least 30 °, particularly preferably at least 45 °. This means that the basic field magnet sections (with respect to their section main field direction) are correspondingly arranged obliquely to one another. In this connection, it is preferred that the basic field magnet sections face each other with one of their side walls, and that the winding or coil planes of adjacent basic field magnet sections are inclined to each other. The side walls are lateral walls in which the current conductors of the magnet winding run. The side walls may also be referred to as edges. Thus, the side wall is not to be understood as an end face of the magnet from which the magnetic field exits and which is, for example, substantially parallel to the coil plane of the magnet coils of the basic field magnet section, but as a side in the main field direction of the section transverse to the basic field magnet section.

Preferably, the basic field magnet arrangement can comprise at least one group of basic field magnet segments, which are arranged in a star-shaped manner about at least one spatial axis, wherein the side walls or edges of the respective basic field magnet segments each point toward the central axis. The arrangement is preferably rotationally symmetrical, wherein a rotational symmetry of 360 °/N (in one group) is particularly preferably present in the case of N basic field magnet sections. In the case of six basic field magnet segments, the basic field magnet arrangement looks like a hexagon star, for example. However, the star can also comprise a partially regular arrangement of the basic field magnet sections, for example such that the basic field magnet sections are all regularly arranged within a semicircle. An arrangement of a plurality of the partially regular stars around a plurality of central or spatial axes is also preferred, for example an arrangement of two semi-circles which are arranged slightly spaced apart from one another, in order to generate the already mentioned basic magnetic field overall, for example in the shape of a ring with an interposed linear channel.

Particularly preferably, the basic field magnet arrangement comprises a basic field magnet section or a group of basic field magnet sections which are configured in such a way that the basic magnet main field direction of the intended basic magnetic field is deflected by a total deflection angle of at least 60 °, preferably at least 90 °, more preferably at least 180 °. Preferably, the segment main field direction of the magnetic field of the basic field magnet segment or the resulting segment main field direction of the resulting magnetic field of the group (i.e. the segment group main field direction) runs here in an arc, which shows a deflection at the angle. The basic field magnet section or the group of basic field magnet sections can be used for the targeted guidance of the basic magnetic field.

In particular, if the basic field magnet segments as described above are arranged in a star shape or in a similar manner around the central axis in order to achieve a ring-shaped closed extension of the basic magnet main field direction of the basic magnetic field, and if the individual basic field magnet segments are designed such that they produce a magnetic field that is substantially homogeneous in the spatial direction perpendicular to their segment main field direction (i.e. if the basic field magnet segments are designed, for example, in the form of helmholtz coils), this can lead to a basic magnetic field whose field strength is inhomogeneous in the radial direction (starting from the central axis) as long as the basic magnetic field is (continuously) reduced. This is due to the fact that the spacing between the individual basic field magnet sections close to the spatial axis is narrower than in the radially larger spacing from the central axis. That is, the density of the field lines of the resulting basic magnetic field decreases radially outwards.

In order in particular to compensate for this and to achieve a basic field that is as homogeneous as possible also in the radial direction, in a preferred embodiment of the basic field magnet arrangement the basic field magnet sections (preferably each of the basic field magnet sections) can have coil windings that generate a desired magnetic field that is stronger towards one side of the basic field magnet section, that is to say in a direction transverse to the section main field direction of the basic field magnet section. For this purpose, the coil windings are preferably designed such that the diameter of one winding is reduced in at least one spatial direction compared to its neighbors and its midpoint lies closer to one side of the annular basic magnetic field. The magnetic field of the individual basic field magnet segments is therefore preferably stronger toward the outer edge of the basic field magnet arrangement (for example toward a circular, in particular annular, outer edge) in order to compensate as well as possible the otherwise occurring radial inhomogeneities of the overall resulting basic magnetic field. With regard to the basic field magnet section, it can also be said that the winding gradually tends towards the outer side wall of the basic field magnet section, i.e. the outer side of the ring shape of the basic field. The exact type or topology of the windings is preferably adapted to the arrangement of the basic field magnet sections in order to achieve a suitable compensation of inhomogeneities.

As mentioned, a preferred variant of the magnetic resonance tomography system comprises a plurality of measurement points (at least two) in the (common) basic field magnet arrangement or in the main field region of the common basic magnetic field. The measurement site is preferably arranged here, in particular in the case of the basic field magnet arrangement described above, between two basic field magnet sections in each case and/or in a patient tunnel in the basic field magnet section.

As already mentioned above, the basic field magnet arrangement of the preferred magnetic resonance tomography system can preferably have a basic field magnet section or a group of basic field magnet sections which are configured in order to deflect the basic magnet main field direction of the expected basic magnetic field by a total deflection angle of at least 60 °, preferably at least 90 °, more preferably at least 180 °. Such a basic field magnet arrangement can also be used in particular in the preferred embodiment described above, in order to deflect the basic magnet main field direction by 180 ° from one measurement location to another, so that the basic magnet main field direction at the measurement location is reversed.

It is particularly preferred that the basic field magnet section or the group of basic field magnet sections is arranged below or above at least one measurement location or at least on one side of a measurement location, wherein preferably the basic field magnet section or the group of basic field magnet sections adjoins two different measurement locations.

In a preferred magnetic resonance tomography system with a plurality of measurement locations, the basic field magnet section (e.g. the basic field magnet) can also preferably be designed as a wall and/or be arranged in a wall between two measurement locations.

A particularly preferred variant comprises a basic field magnet arrangement with a group of basic field magnet sections arranged regularly in a semicircle, which group deflects the basic magnetic field by 180 °, and a further basic field magnet section which is arranged centrally perpendicular to the semicircle (as if standing upright on the semicircle) and can be located between two measurement points. This is also explained in more detail later on according to a preferred embodiment.

Compared to conventional magnetic resonance tomography based on a homogeneous basic magnetic field with rectangular and parallel field lines, the first main variant of the invention allows variants in the art of image recording, in particular signal encoding and image reconstruction. In this case, the signal encoding and image reconstruction follow an "equal frequency plane

", i.e. the faces having the same frequency of the recorded area. The constant frequency surfaces are curved in the ring magnetic field and follow surfaces having respectively the same magnetic field strength.

In the following, a second main variant of the invention is described in more detail, which advantageously uses, in particular, the stray field of the MR system for the measurement.

For this purpose, the preferred magnetic resonance tomography system comprises the following components:

at least one primary measurement site (with infrastructure for MR measurement, at least a measurement coil) which is located within the basic field magnet arrangement, in particular within the basic field magnet or between the windings of two basic field magnets, for example C-magnets. Basic field magnet arrangements are usually of classical construction, such as solenoids or C-magnets, as they are used in conventional MR systems, in which the shielding of the basic magnetic field is (at least partially) abandoned. In this case, there is usually only one primary measurement site. This does not exclude that a basic field magnet arrangement according to one embodiment of the first main variant with a plurality of measurement locations set forth above is also possible, provided that its stray magnetic field is sufficient.

At least one secondary measurement location (with-as mentioned above-at least temporarily, but in other preferred embodiments also permanently-own infrastructure for MR measurements, at least with a measurement coil) which is located outside the basic field magnet arrangement. Preferably, the MR system comprises at least two secondary measurement sites.

According to this second preferred main variant of the magnetic resonance tomography system according to the invention, the secondary measurement site is therefore in the stray field region of the basic field magnet arrangement, so that stray fields of the basic magnetic field are used. For example, in the case of a solenoid as the basic field magnet, this can be achieved by: the basic field magnet, as described above, has no or only a limited shielding and the secondary measurement site is in its stray field next to the basic field magnet. The stray field is at least sufficient for some MR measurements, so that further measurements at the secondary measurement site can be made in parallel with the "primary measurement" at the primary measurement site. Compared to shielded basic field magnets, unshielded basic field magnets are cheaper and smaller, so that economic advantages are increased by dispensing with (strong) shielding.

Similar matters as described above for the ring magnetic field apply to the secondary measurement site, with the difference that: it is not necessary to use additional basic field magnets or basic field magnet sections.

For example, at the at least one secondary measurement site, the resulting field vector of the expected magnetic field stretch (which corresponds more above to the segment main field direction, here now referring only to the stray field of the basic magnetic field) should be inclined at least 30 ° relative to the expected basic magnet main field stretch (e.g. the main field of the solenoid) at the location of the primary measurement site, preferably oppositely inclined.

An advantage of this embodiment or the second main variant is that stray magnetic fields which in the main examination are anyway formed around the scanner can be used simply for the additional examination. Furthermore, the costs for shielding the basic field magnet can be saved additionally, since stray magnetic fields are used precisely. By means of further magnets (e.g. basic field magnet segments), it is possible to perform a "steering" of the basic magnetic field, as described above.

The preferred magnetic resonance tomography system comprises at least two secondary measurement locations arranged on different sides of the primary measurement location, which are preferably in a common plane with the primary measurement location.

Alternatively or additionally, the preferred magnetic resonance tomography system comprises a plurality of secondary measurement locations arranged in a star around the primary measurement location. The secondary measurement site is preferably situated where the extent of the stray field runs antiparallel to the basic magnet main field direction of the expected basic magnetic field at the primary measurement site.

In a preferred magnetic resonance tomography system, at least one measurement location, preferably a secondary measurement location, has a height adjustment device, by means of which the height of all measurement locations and/or of the object to be examined can be adjusted.

In a preferred magnetic resonance tomography system, the secondary measurement site is arranged in a different space (examination space) from the primary measurement site and/or the secondary measurement site is separated from the primary measurement site by a wall. The wall can be a (side) wall, a ceiling or a floor. In this case, it is preferred that the wall between the primary and secondary measurement locations is paramagnetic and/or that a faraday cage is formed around the wall of the measurement location. Alternatively or additionally, the wall is an acoustic separation. As an advantageous embodiment, the wall can also have positionable ferromagnetic elements, which can be set accordingly for passive shimming effects. The wall portions are preferably opaque to provide optical shielding as well.

Particularly preferred are mobile or modular embodiments in which the primary and/or secondary measuring locations can be arranged in different container modules, wherein the containers can be arranged side by side or one above the other. The wall of the container is preferably made of aluminum or plastic. However, the wall portion can also have the above-mentioned positionable ferromagnetic element. Copper mesh introduced or applied into the wall as a faraday cage is also preferred.

Preferably, in a variant of the magnetic resonance tomography system according to the invention, the basic magnet main field direction of the basic magnetic field is oriented perpendicular to the ground in the region of the primary measurement location. The basic field magnet with the patient tunnel is therefore standing on the floor with the end face, and the patient is examined standing and not lying flat. Preferably, a number of secondary measurement points are located in the region around the basic field magnet, wherein the patient can also be examined standing there in particular. Such a device may also sink in the ground, which in turn results in good shielding of the entire system outwards.

In such magnetic resonance tomography systems, in particular, as mentioned, a height adjustment at the measurement location is expedient in order to position the object to be examined in the measurement location.

Preferably, the position of the secondary measurement site is selected or the above-mentioned basic field magnet arrangement for the measurement site is configured such that the magnetic field (whereby the basic magnetic field and in particular also the stray field of the basic magnetic field are referred to herein) is as homogeneous as possible at the measurement site. In order to improve the homogeneity even further, shim coil systems can be used, in particular also at the secondary measurement locations. For this purpose, it is also possible to use prior art methods or principles of conventional magnetic resonance tomography systems, which can be adjusted in a suitable manner if necessary. By means of a gradient system which can also be present at each measurement location or which belongs to each measurement device, the desired gradient field for the measurement can then be applied.

In a further preferred embodiment, however, it is also possible to use the currently known or well-defined inhomogeneities of the basic magnetic field in a targeted manner, for example for the location coding of the measurement data or the raw data.

In this respect, in particular in the case of the basic field magnet arrangement described above with a circularly extending basic magnetic field, it is possible to make full use of: in the case where the magnetic field extends in a loop shape, as described above, there is generally a stronger magnetic field toward the midpoint of the loop than at the edge without an appropriate countermeasure. Generally, the decrease in field strength is inversely proportional to the spacing from the midpoint of the ring. Since inhomogeneities of the magnetic field, which were, however, usually set up by gradient coil systems, are usually used for the location coding in the context of MR measurements, the inhomogeneities of the basic magnetic field, which are produced by the design of the basic field magnet arrangement, can be used advantageously. At least it is not necessary, as has been done hitherto in the prior art, to apply a gradient field in the direction of the inhomogeneities.

It should be mentioned additionally that combinations of different variants are also possible, i.e. for example inhomogeneities of the basic magnetic field are used only in some spatial directions, and additional gradient fields are used in some spatial directions, or these are also processed differently between the measurement locations.

Preferably, no whole-body coil (i.e. a whole-body coil in the form of an RF coil, a magnet coil or a gradient coil) is used at the secondary measurement site, but only local receive and transmit coils are used. This has the following advantages: the wall of the measuring site can be formed very thin. When using a gradient system, for example, only the gradient coils should also be arranged in the wall. It is also advantageous to arrange gradient coils in the examination table, which are known as "local orthogonal plane gradient coils". In a further preferred embodiment, the measurement site does not have a gradient system, but rather a matrix of transmit/receive coils which are used for site coding in addition to their measurement function.

According to a preferred method, it is therefore also within the scope of the invention to position at least one object in a secondary measurement location (also referred to as "satellite measurement location" in the following) and to measure raw data for the magnetic resonance tomography recording at the secondary measurement location. This is preferably achieved by means of a measuring device according to the invention, which is preferably mobile. It is particularly advantageous if the measurements for the magnetic resonance tomography recording are performed simultaneously at least two measurement locations. As already indicated above, it is not absolutely necessary here for: raw data measurements or RF excitations are performed simultaneously, which may also be coordinated alternately. According to a particularly preferred method, the inhomogeneity of the basic magnetic field, in particular of the stray magnetic field at the secondary measurement location, is used here for the location coding of the raw data.

With the aid of the invention, the satellite measuring location can preferably also be designed such that it is optimized specifically for the specific examination. For example, a secondary measurement site dedicated to breast examinations or head examinations is shaped as a chair with a dedicated support comprising measurement coils and/or gradient coils. It is also preferred to provide a gynecological measuring site or a measuring site for prostate examination with an invasive RF probe and an anatomically adapted gradient system. Further examples are neurological examinations, cardiac examinations, renal examinations, abdominal examinations, angiograms and musculoskeletal examinations. Furthermore, an interventional examination can be performed well in the secondary measurement site.

Drawings

The invention is explained in detail again below with reference to the figures according to embodiments. In the different figures, identical components are provided with the same reference numerals. The figures are generally not to scale. The figures show:

figure 1 shows a schematic view of a magnetic resonance tomography system according to the prior art,

figure 2 shows a simplified diagram of an embodiment of a magnetic resonance tomography system with a first preferred basic field magnet arrangement,

figure 3 shows a schematic view of a basic field magnet arrangement as can be used in the embodiment according to figure 2,

figure 4 shows a somewhat more detailed view of a basic field magnet arrangement as can be used in the embodiment according to figure 2,

figure 5 shows a further embodiment of a magnetic resonance tomography system with a preferred basic field magnet arrangement,

figure 6 shows a further embodiment of a magnetic resonance tomography system with a preferred basic field magnet arrangement,

figure 7 shows a further embodiment of a magnetic resonance tomography system with a preferred basic field magnet arrangement,

figure 8 shows a schematic view of a preferred coil winding as can be used for example in the basic field magnet arrangement according to figures 1 to 7,

fig. 9 shows a detailed view of a basic field magnet arrangement similar to that in fig. 2, but now with coil windings as in fig. 8,

figure 10 shows a magnetic resonance tomography system with two secondary measurement sites according to another embodiment of the invention,

figure 11 shows a further embodiment of a magnetic resonance tomography system according to the invention with a total of four secondary measurement locations,

figure 12 shows a further embodiment of a magnetic resonance tomography system according to the invention which likewise has a total of four secondary measurement locations,

fig. 13 shows a further exemplary embodiment of a magnetic resonance tomography system according to the present invention, which has a star-shaped arrangement of a total of six secondary measurement locations in the upright position,

figure 14 shows a schematic very simple block diagram of a measuring device according to the invention,

fig. 15 shows a mobile or modular embodiment of the MR system in the container device.

Only elements that are important to or helpful in understanding the present invention are depicted in the following figures.

Detailed Description

A magnetic resonance tomography system 1 is shown roughly schematically in fig. 1. On the one hand, the magnetic resonance tomography system comprises a real magnetic resonance scanner 2 with a measurement site 3 or an examination space 3, here a conventional patient tunnel 3, in which a patient O or a subject, that is to say an examination object O, is positioned on a bed 8. However, usually not the entire patient O is scanned, but only a region of interest within the patient O, that is to say only raw data are measured from said region.

The magnetic resonance scanner 2 is equipped in a conventional manner with a basic field magnet system 4, a gradient system 6 and an RF transmit antenna system 5 and an RF receive antenna system 7. In the illustrated embodiment, the RF transmit antenna system 5 is a whole-body coil fixedly enclosed in the magnetic resonance scanner 2, while the RF receive antenna system 7 is constituted by a local coil to be disposed at the patient or subject. In principle, however, the whole-body coil can also be used as an RF receiving antenna system and the local coil as an RF transmitting antenna system, provided that the coils can be switched into different operating modes. The basic field magnet system 4 is designed in a conventional manner such that it generates a basic magnetic field in the longitudinal direction of the patient, that is to say along the longitudinal axis of the magnetic resonance scanner 2 extending in the z direction. The gradient system 6 comprises in a conventional manner individually controllable gradient coils in order to be able to switch the gradient independently of one another in the x, y or z direction. Furthermore, the magnetic resonance scanner 2 can have shim coils (not shown) which can be designed in a conventional manner.

The magnetic resonance tomography system 1 also has a central control device 13 for controlling the MR system 1. The central control device 13 comprises a sequence control unit 14. By means of the sequence control unit, the order of the radio frequency pulses (RF pulses) and gradient pulses is controlled in relation to the order of a plurality of pulse sequences or selected pulse sequences for recording a plurality of slices in a volumetric region of interest of the examination object within a measurement session. Such a pulse sequence can be preset and parameterized, for example, within a measurement or control protocol. Typically, different control protocols for different measurements or measurement sessions are saved in the memory 19 and can be selected by the operator (and possibly changed if required) and then used to perform the measurements. In the present case, the control device 13 comprises a pulse sequence for measuring the raw data, i.e. for exciting the MR signals used for acquiring the raw data.

For outputting the individual RF pulses of the pulse sequence, the central control device 13 has a radio-frequency transmission device 15, which radio-frequency transmission device 15 generates, amplifies and feeds the RF pulses into the RF transmission antenna system 5 via a suitable interface (not shown in detail). In order to control the gradient coils of the gradient system 6 in order to appropriately switch the gradient pulses corresponding to a preset pulse sequence, the control device 13 has a gradient system interface 16. The sequence control unit 14 communicates with the radio frequency transmission means 15 and the gradient system interface 16 in a suitable manner, for example by transmitting sequence control data SD, to execute the pulse sequence.

The control device 13 also has a radio-frequency receiving device 17 (likewise in a suitable manner in communication with the sequence control unit 14) in order to receive magnetic resonance signals in a coordinated manner within a read window preset by the pulse sequence by means of the RF receiving antenna system 7 in order to acquire the raw data.

Here, a reconstruction unit 18 receives the acquired raw data and reconstructs magnetic resonance image data therefrom. The reconstruction is usually also performed on the basis of parameters that can be preset in the respective measurement or control protocol. The image data can then be saved, for example, in the memory 19.

How to be able to acquire suitable raw data by injecting RF pulses and switching gradient pulses and to reconstruct MR images or parameter cards therefrom in detail is known in principle to the person skilled in the art and is therefore not explained in detail here.

The central control device 13 can be operated via a terminal 11 with an input unit 10 and a display unit 9, via which the entire magnetic resonance tomography system 1 can therefore also be operated by an operator. On the display unit 9, the magnetic resonance tomography images can also be displayed, and by means of the input unit 10, possibly in combination with the display unit 9, the measurement can be planned and started, and in particular the control protocol can be selected and, if necessary, modified.

Furthermore, such a magnetic resonance tomography system 1 and in particular the control device 13 can also have a large number of further components which are not shown in detail here but are usually present at such a facility, such as, for example, a network interface, in order to connect the entire system to a network and to be able to exchange raw data and/or image data or parameter cards, but also other data, such as, for example, patient-relevant data or control protocols.

Fig. 2 shows an embodiment of a magnetic resonance tomography system 1 according to a first main variant of the invention with a preferred basic field magnet arrangement 40, in which a plurality of measurement locations can be used in the main field region of the basic magnetic field of the basic field magnet arrangement 40.

A magnetic resonance scanner 2 is shown here, the function of which can be controlled by a control device 13. The control device 13 can in principle be constructed in a similar manner and have the same components as the control device 13 in the conventional MR system according to fig. 1. Likewise, the control device can also have suitable terminals or the like (however, this is not shown here).

The basic field magnet arrangement 40 of the magnetic resonance scanner 2 comprises six (in this case identical) basic field magnet sections 44, which are arranged in a star-shaped manner about the center axis a in the embodiment described with a rotational symmetry of 60 °. The basic magnetic field B0 indicated by an arrow has a basic field main direction R0 which extends in the form of a circular or ring-shaped magnetic field.

Fig. 3 shows a detailed schematic illustration of the individual basic field magnet segments 44 of the star-shaped basic field magnet arrangement 40 from fig. 2.

Here, six helmholtz coils are visible as basic field magnet sections 44 of the basic field magnet arrangement 40. The helmholtz coil is oriented with its coil plane or winding plane edge toward the center axis a. Each individual basic field magnet section 44 has a section main field direction R1 (shown in the view in fig. 2 in only one of the last two basic field magnet sections 44) which corresponds to the expected magnetic field of the (relatively short) solenoid, that is to say the magnetic field generated by the individual basic field magnet section 44, runs perpendicular to the end faces of the basic field magnet section 44 concerned and tangentially to the basic magnet main field direction R0. The individual magnetic fields of the basic field magnet segments 44 jointly result in a basic magnetic field B0 shown in fig. 2 with a ring-shaped basic magnet main field direction R0, wherein the segment main field direction R1 is "tangent" to the circular basic magnet main field direction R0 in each case at the midpoint of the individual basic field magnet segments 44. The basic magnetic field B0 decreases outward in the radial direction, but is uniform in height.

The basic field magnet sections 44 of the basic field magnet arrangement 40 are connected to one another in such a way that a direct current flows from one basic field magnet section 44 to the next, wherein the direction of the current flow through the magnet windings is always the same and, by means of the current flow, a circular magnetic field B0 is formed overall.

A significant advantage of this symmetrical arrangement is the structural stability when the basic magnetic field B0 is switched on. The magnetic forces between the individual basic field magnet sections 44 cancel out oppositely in the direction of the basic magnet main field direction R0. Each basic field magnet segment 44 is attracted by its two neighbors, respectively, with the same force. The resulting forces act inwardly towards the column 43 and can be compensated very well there by corresponding structural reinforcements.

A cross section through the basic field magnet section 44 is shown in an enlarged manner in the upper left corner of fig. 3. A regular arrangement of the current conductors 21, which are drawn here as lines, can be seen, but can quite have a complex construction, for example can be hollow, in order to lead through the coolant.

Such a magnetic resonance tomography system 1 with the basic field magnet arrangement 40 according to fig. 2 and 3 allows measurements to be taken at six different measurement locations M1, M2, M3, M4, M5, M6 (see fig. 2), wherein in the example shown the measurement of the object O takes place exactly at the measurement location M4, wherein the patient stands upright here at the vertical wall of the basic field magnet arrangement 40. In principle, measurements can be carried out simultaneously at all six measurement locations M1, M2, M3, M4, M5, M6. The central column 43 holds the basic field magnet section 44 at its location and can also comprise technical components, such as for example electrical connections or even power supply means (see for example fig. 4).

At the measurement locations M1, M2, M3, M4, M5, M6, there can be a measurement device 12 (only shown symbolically in each case) or components required for this at the measurement locations M1, M2, M3, M4, M5, M6, such as an RF transmitter coil of an RF transmitter system, an RF receiver coil of an RF receiver system and/or a common RF transmitter/receiver coil. Likewise, gradient coils and/or shim coils 6a can also be included therein. All the components can be operated in a coordinated manner by a common control device 13.

Of course, the magnetic resonance scanner 2 can also have more than six measurement locations M1, M2, M3, M4, M5, M6, the height of which can be lower, or which is designed for examining smaller body regions, for example for head examinations or examinations of limbs, female breasts, prostate, liver, kidney or other organs. The star-shaped basic field magnet arrangement 40 can also be positioned lying flat.

Fig. 4 shows an embodiment of a magnetic resonance tomography system 1 with a superconducting basic field magnet arrangement 40. This can be a superconducting version of the embodiment shown in fig. 2. To better illustrate the internal configuration, the front two basic field magnet sections 44 are not shown. It can be seen that the basic field magnet arrangement 40 is filled with helium He, which is partly liquid and partly gaseous. Here, the reference numeral of helium He points to the liquid level. The entire basic magnetic field arrangement 40 is surrounded by the housing wall 30, which in this case has, in particular, a thermal insulation, whereby the helium He in the housing interior 33 is kept cold and thus in a liquid state.

Such an insulation can for example comprise a multilayer insulating film or a thermally conductive shield against ambient thermal radiation.

In the upper part of the middle of the basic field magnet arrangement 40, a cooling unit 22 is arranged, at whose cooling fingers 22a helium He continuously condenses and drops downward. The helium content and pressure in the basic field magnet device 40 can be adjusted through the helium line 22 b. In the lower part, a magnet lead distributor 20 (english) is visible at a switching unit 23, which can supply the basic field magnet arrangement 40 with current via a current supply line 24. The switching unit 23 can be used as a permanent switch in order to generate a continuously circulating current in the superconducting basic field magnet arrangement 40 and thus a permanent basic magnetic field B0.

However, other cooling alternatives are also possible, for example by means of liquid helium being led through the hollow conductor of the magnet or through additional cooling lines in good thermal contact with the magnet coil. In the design of the basic field magnet arrangement 40, further components can also be included, which are not drawn here for the sake of overview, such as Quench detectors or Quench protectors (Quench-Detektor bzw. -Schutz), so-called "coil formers" (magnet formers) or structural reinforcements.

Figure 5 shows a further embodiment of a magnetic resonance scanner 2 with a preferred basic field magnet arrangement 40. In this case, only the lower half of the basic field magnet arrangement 40 is formed in a star shape as a group 41 of basic field magnet sections 44, and the other basic field magnet section 44 projects upward and serves both for guiding the basic magnetic field B0 and as a part of the wall W between the two measurement points M1, M2, at which the two patients O are located. In the illustration, it can be seen that the lower part of the wall W between the two patients O is formed by the housing wall 30 of the magnetic resonance scanner 2, into which the basic field magnet section 44 between the measurement points M1, M2 is integrated. The wall portion W can be used not only as a sight line protection but also as an acoustic shield or an RF shield.

The basic magnetic field B0 of the magnetic resonance scanner 2 is weakened outwards, which can be used for location coding and is homogeneous in the longitudinal direction (orthogonal to the drawing plane). In principle, the two measuring points M1, M2 are identical in shape, the only difference being that the extent (in the direction across the surface on which the patient O is supported) is opposite. In this case, as in fig. 2, the dimensions of the magnetic resonance scanner 2 can also be selected completely differently.

Here, too, the basic magnet main field direction R0 is circular. A feature in the described embodiment is that the patient O is not lying flat in a narrow space, but is able to look freely to the ceiling. As mentioned, inhomogeneities in the basic magnetic field B0, which are usually caused by bending, can be used for spatial-directional location coding, so that for overall location coding only gradients in other spatial directions have to be applied.

This arrangement allows easy and less restrictive access to the patient due to its open construction and the annular magnetic field. By means of a special design, as in fig. 2, the magnetic force is largely compensated or guided out into a region that can be reinforced in a structurally favorable manner.

Figure 6 shows a further embodiment of a magnetic resonance scanner 2 with a preferred basic field magnet arrangement 40. The basic field magnet arrangement is constructed similarly to the basic field magnet arrangement in fig. 5, with the difference that: above and below the two measurement points M1, M2, there are now

groups

41, 42 of basic field magnet sections 44. As can be seen from the plotted extension of the magnetic field lines, the expected extension of the basic magnetic field B0 is very uniform here in the region of the measurement points M1, M2.

The housing 30 comprises upper and lower semi-cylindrical housing sections 30u, 30o, each having a cross section in the form of a 180 ° circle section in which the basic field magnet sections 44 of the

respective group

41, 42 are arranged. The

groups

41, 42 of basic field magnet sections 44 are held at a distance from one another by means of intermediate webs or limiting elements 31 which are part of the housing 30, the half-columns of the housing sections 30u, 30o each facing one another with their flat sides, so that two measuring points M1, M2 are provided between the housing sections 30u, 30 o. The lower semi-cylindrical housing section 30u stands on the base 35, and the upper semi-cylindrical housing section 30o can additionally be held at the ceiling holder 36. The delimiting element 31 here simultaneously serves as a separating wall or wall W between the two measuring points M1, M2.

In contrast to the configuration of fig. 5, the configuration shown here has the following purpose: a homogeneous magnetic field is generated at the two measurement points M1, M2. The spatial openness of such a magnetic resonance scanner 2 is similar to a C-shaped magnet system, but unlike such a C-shaped magnet system, no solid iron yoke is required for shielding or deflecting the magnetic field lines. Instead of this, the

groups

41, 42 of basic field magnet sections 44 serve to shield and divert the basic magnetic field B0, which considerably reduces the weight.

Fig. 7 shows a further exemplary embodiment of a magnetic resonance tomography system 1 with a preferred basic field magnet arrangement 40. The magnetic resonance tomography system is very similar to the configuration of figure 6, except that: in this case, four measurement points M1, M2, M3, M4 are now present at the location of the two measurement points. Two of the measuring points M1, M2, M3, M4 are arranged one above the other, wherein the upper measuring point and the lower measuring point are each separated by the bottom element 32 of the housing 30. The base element 32 simultaneously serves as a receptacle for the basic field magnet section 44, which guides the magnetic field in the magnetic resonance scanner 2 uniformly through the measurement points M1, M2, M3, M4. The base element 32 can be anchored, for example, to an intermediate web or limiting element 31 of the housing 30 serving as a separating wall or wall W between respectively adjacent measuring points M1, M2, M3, M4, or can extend laterally therefrom.

Fig. 8 shows a schematic illustration of a coil winding 25 made of current conductors 21 for compensating inhomogeneities in the toroidal magnetic field, as it can be used within the scope of the invention. It is conceivable for the windings to be present in the opposite basic field magnet sections 44 in fig. 3. As can be clearly seen, the coil windings 25 are constructed such that the diameter of one winding is reduced in one spatial direction (i.e. in this horizontal line) compared to its neighbouring windings and its centre point is closer to the outer edge of the annular basic magnetic field B0 than to the centre point of the larger winding. Thereby generating a desired magnetic field (of the respective one of the basic field magnet sections 44) which is stronger towards the outside of the basic field magnet sections 44, respectively. As a result, the inhomogeneities of the basic magnetic field B0, which are described in conjunction with fig. 2, 3 and 5 and which extend in the radial direction, can be compensated for at least partially, preferably completely, in a suitable configuration.

Fig. 9 shows a schematic illustration of the embodiment shown in fig. 2 with the coil winding 25 according to fig. 8 from above. Here, only the basic field magnet section 44 is provided with a detailed illustration. It should be assumed that all further basic field magnet sections 44 are also constructed in this way.

The density of the current conductors 21 can also increase as the radial spacing increases.

The coil windings 25 are arranged in the housing interior 33 of the housing 30. Since the number of current conductors 21 (only one is depicted for the sake of overview) is very high at the edges and the density is otherwise regular over the width of the basic field magnet section 44, the basic field magnet arrangement 40 has a thickening at the outer end sections 34 of the side walls of the basic field magnet section 44, in which the current conductors are guided in a bundle.

In accordance with the following figures, different embodiments are now each illustrated very schematically, in which a "secondary" measurement location Ms or a "satellite measurement location" is used, as already mentioned above, which is in the unshielded or at most weakly shielded stray field of the basic magnetic field of the basic field magnet arrangement. A "primary" measurement site Mp is present in the basic field magnet arrangement itself or in the main field region of the basic magnetic field, respectively.

Fig. 10 shows a first exemplary embodiment of such a magnetic resonance tomography system 1 according to the present invention. The primary measurement point Mp is in this case in a relatively simple basic field magnet arrangement 40, for example with only one basic field magnet in the form of a (in particular superconducting) solenoid. As a result, a very homogeneous basic magnetic field B0 is generated at the primary measurement location Mp, by means of which very precise measurement by means of the measuring device 12p is possible. In principle, the basic field magnet of the basic field magnet arrangement 40 can be constructed like the basic field magnet 4 in fig. 1, except for a modified or partially non-existent magnetic field shield. All further components can also be present at the primary measurement site Mp, as already explained in the context of fig. 1.

Outside the basic field magnet arrangement 40, fig. 10 shows a stray magnetic field Bs, in which two secondary measurement sites Ms are arranged. All components can also be present at the secondary measurement site, as already explained in the context of fig. 1, except for the further basic field magnet 4. The "satellite measurement site" Ms has, inter alia, a measuring device 12 a.

In the case of a basic field of 3T in a distance of 1.5m, a shielded conventional basic field magnet always also has a field strength of 50mT in the stray field Bs. If the shielding is omitted here as in the case of the basic field magnet arrangement 40, the strength in the stray magnetic field Bs increases significantly. For example, a field strength of approximately 0.5T is still present in a distance of 1m or a field strength of approximately 100mT is still present in a distance of 4m at the satellite measurement location Ms.

The two satellite measurement sites Ms can have a much larger patient tunnel (e.g. 80cm) and a shorter construction (e.g. 1m) than the primary measurement site Mp. This advantageously acts on anxiety avoiding claustrophobia.

For example, if an unshielded gradient system 6 is used, the wall thickness of the satellite measurement site Ms can be thinner. This is possible because the person is relatively far from the basic field magnet arrangement 40.

In order to compensate for undesired inhomogeneities in the stray field Bs, the secondary measurement site Ms can have a shim coil system 6a (shown only at the rear satellite measurement site Ms in fig. 10). This can be a separate coil system or be realized in the context of a gradient system 6 (see fig. 1).

Fig. 11 shows a further exemplary embodiment of a magnetic resonance tomography system 1 according to the present invention. In addition to the primary measurement site Mp, four secondary measurement sites Ms are provided here, so that the stray magnetic field Bs of the basic field magnet arrangement 40 of the primary measurement site Mp can be used for measurement at the secondary measurement sites Ms. The measurement sites Mp, Ms are separated from each other by a wall W (side wall or ceiling) and are both in different spaces here, so that privacy can be protected. The wall W is preferably constructed as a faraday cage in order to avoid RF cross-talk. Additionally, the wall also serves as an advantageous sound insulation and optical shielding.

In order to place the upper two secondary measuring locations Ms in the region of the largest possible field strength of the stray magnetic field Bs, said secondary measuring locations can be lowered for measurement into the pit (arrow) via the height adjustment device 26.

With such a device, up to five patients can be examined simultaneously, wherein of course the best results are achieved at the primary measurement site MP. As in the arrangement already described above, the basic field magnet 4 does not require a shield, and the patient tunnel of the secondary measurement site Ms can be constructed larger, i.e. with a measurement range of greater diameter and shorter length extension.

Fig. 12 shows a further exemplary embodiment of a magnetic resonance tomography system 1 according to the present invention. This embodiment is very similar to fig. 11, with the difference that here the primary measuring location Mp is at the top and the two secondary measuring locations Ms at the bottom can be lifted upwards by means of the height adjusting device 26.

The height adjustment device 26 can be realized, for example, by a pneumatic actuator, which is preferably automatically controlled.

Such a height adjustment device 26 also allows MR recordings with different Field strengths, in particular for methods known as "Field cycling", and enables very good imaging of the distribution of the contrast agent in the patient.

Fig. 13 shows a further exemplary embodiment of a magnetic resonance tomography system 1 according to the present invention, which has an upright primary measurement location Mp and six likewise upright secondary measurement locations Ms arranged in a star-shaped manner around the primary measurement location. With this arrangement, for example, an examination of the spine can be achieved.

By means of the height adjustment device 26, the patient can reach the measurement locations Mp, Ms, for example on a platform or by means of a vertical "examination bed" provided exclusively with a holding device. Then, after the measurement, the patient can be lifted upwards again.

Fig. 14 shows a rough schematic block diagram of a measuring device 12s according to the invention, as it can be arranged, for example, at a satellite measuring location Ms. The measuring device includes: an RF transmission system having an RF transmission antenna system 5 and a radio frequency transmission device 15; an RF receiving system having an RF receiving antenna system 7 and a radio frequency receiving device 17; a sequence control unit 14 and a reconstruction unit 18. The measuring device in principle does not require a unit for generating its own basic magnetic field, for example a U-shaped magnetic field of a permanent magnet, since it is able to use the stray magnetic fields of existing basic field magnet arrangements. The measuring device can also be designed to be movable in order to temporarily equip different secondary measuring locations with measuring devices, for example, the measuring device can be designed as a portable device, which is comfortable in the hand, for example.

Fig. 15 shows a mobile or modular embodiment of the MR system 1 in a container. The secondary measurement site Ms can be located beside the container, for example in a further container (indicated with dashed lines). The container should not have ferromagnetic walls, whereby the stray magnetic field Bs can reach the secondary measurement site well. By this modular construction by means of the container, the treatment space according to fig. 11 or 12 can be realized very simply and quickly.

Finally, it is again pointed out that the method described in detail above and the magnetic resonance tomography system 1 or the measuring device shown are merely embodiments which can be modified in different ways by a person skilled in the art without departing from the scope of the invention. Thus, for example, as already mentioned, depending on how the basic magnetic field is constructed and shielded or even intentionally not shielded, it is also possible to provide additional satellite measurement sites in stray fields (as is the case in the second main variant of the invention) at a magnetic resonance tomography system with a plurality of (primary) measurement sites in the main field region of the basic magnetic field or in the basic field magnet arrangement itself (as is the case in the first main variant of the invention). Furthermore, the use of the indefinite article "a" or "an" does not exclude that a feature referred to can also be present several times. Likewise, the terms "unit" and "device" do not exclude that a component is composed of a plurality of interacting sub-components, which may also be spatially distributed if desired.

Claims

1. A magnetic resonance tomography system (1) comprising a basic field magnet arrangement (40) for generating a basic magnetic field (B0) and a plurality of spatially separated measurement locations (M1, M2, M3, M4, M5, M6, Mp, Ms), wherein the magnetic resonance tomography system (1) is designed to use an expected basic magnetic field (B0) jointly for the measurement locations (M1, M2, M3, M4, M5, M6, Mp, Ms).

2. The magnetic resonance tomography system (1) as claimed in claim 1, which is designed for enabling a simultaneous magnetic resonance tomography recording in a common basic magnetic field (B0) at least two of the measurement locations (M1, M2, M3, M4, M5, M6, Mp, Ms).

3. The magnetic resonance tomography system (1) of claim 1 or 2,

wherein the basic field magnet arrangement (40) has a plurality of basic field magnet segments (44) which are spatially separated from one another in order to generate a respective desired magnetic field with a defined segment main field direction (R1),

wherein at least two of the basic field magnet sections (44) are arranged relative to one another in such a way that the section main field directions (R1) of the expected magnetic fields of the at least two basic field magnet sections run at a deflection angle to one another in such a way that the expected magnetic fields of the basic field magnet sections (44) result in an expected basic magnetic field (B0), wherein the basic magnetic field (B0) has a circularly running basic magnet main field direction (R0).

4. The magnetic resonance tomography system (1) as claimed in any one of the preceding claims, comprising:

-at least one primary measurement site (Mp) within the basic field magnet arrangement (40)

And

-at least one secondary measurement location (Ms) outside said basic field magnet arrangement (40).

5. The magnetic resonance tomography system (1) of claim 4,

wherein the secondary measurement location (Ms) is in the region of a stray magnetic field (Bs) of the basic field magnet arrangement (40).

6. The magnetic resonance tomography system (1) as claimed in claim 4 or 5, comprising:

at least two secondary measurement locations (Ms) arranged on different sides of the primary measurement location (Mp), the secondary measurement locations preferably lying in a common plane with the primary measurement location (Mp),

and/or

A plurality of secondary measurement locations (Ms) arranged in a star around the primary measurement location (Mp).

7. The magnetic resonance tomography system (1) of any one of the preceding claims,

wherein at least one measuring location (M1, M2, M3, M4, M5, M6, Mp, Ms), preferably a secondary measuring location (Ms), has a height adjusting device (26), by means of which the height of all measuring locations (M1, M2, M3, M4, M5, M6, Mp, Ms) and/or objects can be adjusted.

8. The magnetic resonance tomography system (1) of any one of the preceding claims 4 to 7,

wherein at least one secondary measurement location (Ms) is arranged in a different space from the primary measurement location (Mp) and/or is separated from the primary measurement location (Mp) by a wall (W),

wherein said wall (W) between said primary measurement location (Mp) and said secondary measurement location (Ms) is preferably a paramagnetic and/or an acoustic and/or an optical separation, and/or said wall forms a Faraday cage around the measurement location.

9. The magnetic resonance tomography system (1) of any one of the preceding claims 4 to 8,

wherein in the region of the primary measurement location (Mp) the basic magnet main field direction (R0) of the basic magnetic field (B0) is oriented perpendicular to the ground.

10. The magnetic resonance tomography system (1) as claimed in one of the preceding claims, comprising at least two, preferably mutually independent, measuring devices (12p, 12s), wherein each of the measuring devices (12p, 12s) is designed for carrying out a measurement within the magnetic resonance tomography range at one of the measuring locations (M1, M2, M3, M4, M5, M6, Mp, Ms), wherein preferably at least one of the measuring devices (12s) is constructed mobile.

11. The magnetic resonance tomography system (1) of claim 10,

wherein the measuring device (12s) for the secondary measurement location (Ms) comprises at least one RF transmission system (5, 15) and an RF reception system (7, 17), and preferably additionally a gradient system (6) and/or a shim coil system.

12. A measuring device (12p, 12s) for use in a magnetic resonance tomography system (1) according to the preceding claim, having at least one RF transmit system (5, 15) and an RF receive system (7, 17), and preferably additionally a gradient system (6) and/or a shim coil system,

the measuring device (12p, 12s) is preferably designed as a mobile measuring device (12 s).

13. A method for measuring raw data recorded by a magnetic resonance tomography, the method comprising the steps of:

-positioning at least one object in a measurement location (M1, M2, M3, M4, M5, M6, Mp, Ms) of a magnetic resonance tomography system (1) as claimed in any one of claims 1 to 11,

-generating a basic magnetic field (B0) by means of a basic field magnet arrangement (40) of the magnetic resonance tomography system (1),

-measuring said raw data.

14. The method of claim 13, wherein the first and second light sources are selected from the group consisting of,

wherein at least one object is positioned in a secondary measurement location (Ms) and raw data for magnetic resonance tomography recording are measured at the secondary measurement location (Ms), preferably by means of a preferably mobile measuring device (12p, 12s) according to claim 12, wherein preferably magnetic resonance tomography recording is performed simultaneously at least two measurement locations (M1, M2, M3, M4, M5, M6, Mp, Ms).

15. The method according to claim 13 or 14,

wherein inhomogeneities of the stray magnetic field (Bs) of the basic magnetic field (B0), in particular at the secondary measurement location (Ms), are used for location encoding of the raw data.